1. Field of the Invention
The present invention relates to a hinge mechanism of a fluid displacement apparatus. More particularly, it relates to a configuration of a hinge mechanism of a swash plate-type refrigerant compressor for use in automotive air conditioning systems.
2. Description of the Related Art
Generally, the compressor of an automobile air conditioner is driven by the engine of the automobile. The rotation frequency of the drive mechanism of the engine changes with time. The refrigerant capacity changes in proportion to the rotation frequency of the engine. Because the capacity of the evaporator and the condenser of the air conditioner does not change, when the compressor is driven at high rotation frequency, the compressor performs inefficiently. To avoid inefficiency, existing automobile air conditioning compressors are controlled by intermittent operation of the magnetic clutch. However, this results in a large load being intermittently applied to the automobile engine,
One solution, to above mentioned problem is to control the capacity of the compressor in response to refrigeration requirements. One embodiment adjusts the capacity of a compressor, particularly a wobble plate-type compressor, as disclosed in the U.S. Pat. No. 4,664,604 to Terauchi. With reference to FIGS. 1 and 2, a refrigerant compressor includes a closed cylinder housing assembly 100 formed by annular casing 21, which has a cylinder block 23 and a hollow portion with a crank chamber 15, a front end plate 20, and a rear end plate 22. Front end plate 20 is mounted on the left end opening of annular casing 21 and closes the end of crank chamber 15. Front end plate 20 is fixed on annular casing 21 by a plurality of bolts (not shown). Rear end plate 22 and valve plate 24 are mounted on the opposite end of casing 21 by a plurality of bolts (not shown) to cover the end portion of cylinder block 23. An opening 20a is formed in front end plate 20 and receives drive shaft 3. An annular sleeve 20b projects from the front end surface of front end plate 20 and surrounds drive shaft 3 to define a shaft seal cavity 199. A drive shaft seal assembly 202 is assembled on drive shaft 3 within shaft seal cavity 199.
Drive shaft 3 is rotatable and supported by front end plate 20 through bearing 200. Bearing 200 disposed within opening 20a. The inner end of drive shaft 3 is provided with a rotor plate 9. Thrust needle bearing 201 is placed between the inner surface of front end plate 20 and the adjacent axial surface of rotor plate 9 to receive thrust load that acts against rotor plate 9. Thrust needle bearing 201 ensures smooth motion. The outer end of drive shaft 3 extends outwardly from sleeve 20b and is driven by the engine of a vehicle through a conventional pulley arrangement. The inner end of drive shaft 3 extends into a central bore 230 in the center portion of cylinder block 23 and is rotatably supported by a bearing, such as radial needle bearing 232. The axial position of drive shaft 3 may be adjusted by adjusting screw 233, which is screwed into a threaded portion of central bore 230. A spring device 234 is disposed between the axial end surface of drive shaft 3 and adjusting screw 233. A thrust needle bearing 235 is placed between drive shaft 3 and spring device 235 to ensure smooth rotation of drive shaft 3.
A spherical bush 8 is placed between rotor plate 9 and cylinder block 23. Spherical bush 8 may be slidably carried on drive shaft 3. Spherical bush 8 supports a slant or swash plate 4 for nutational (wobble) and rotational motion. A coil spring 10 surrounds drive shaft 3 and is placed between the end of rotor plate 9 and one axial surface of spherical bush 8 to push spherical bush 8 toward cylinder block 23.
Swash plate 4 is connected to rotor plate 9 with a hinge coupling mechanism that rotates in unison with rotor plate 9. Rotor plate 9 has an arm portion 9a projecting axially outward from one side surface. Swash plate 4 also has second arm portion 13 projecting toward arm portion 9a of rotor plate 9 from one side surface. As depicted in FIG. 1, second arm portion 13 is formed separately from swash plate 4 and is fixed on one side surface of swash plate 4. Arm portions 9a and 13 overlap each other and are connected to one another by a pin 11. Pin 11 extends into a rectangular shaped hole 13a, and into arm portion 9a of rotor plate 9. Pin hole 13a is formed through second arm portion 13 of swash plate 4. Thus, rotor plate 9 and swash plate 4 are hinged together. Pin 11 is slidably disposed in rectangular hole 13a. The sliding motion of pin 11 within rectangular hole 13a changes the slant angle of the inclined surface of swash plate 4.
Cylinder block 23 has a plurality of annular arranged cylinders 231 wherein pistons 50 slide. A typical arrangement may have five cylinders 231, but a different number of cylinders 231 may be provided. Each piston 50 comprises a head portion 50a slidably disposed within one of cylinders 231, a hollow portion 50b formed within head portion 50a, a connecting portion 52 and a rod portion 51. Rod portion 51 joins head portion 50a to connecting portion 52. Connecting portion 52 of piston 50 has a cutout portion 52a which straddles the outer peripheral portion of swash plate 4. Semi-spherical thrust bearing shoes 6 are disposed on each side of swash plate 4 and face the inner surface of connecting portion 52. This allows for sliding along the side surface of swash plate 4. The rotation of drive shaft 3 causes the swash plate 4 to rotate between bearing shoes 6 and to move the inclined surface axially to the right and left. The rotation of drive shaft 3 also reciprocates each piston 50 within cylinders 231.
Rear end plate 22 encloses a suction chamber 220 and discharge chamber 221. Valve plate member 24 and rear end plate 22 are fastened to cylinder block 23 by screws. A plurality of valved suction ports 24a may be connected between suction chamber 220 and cylinders 231, and a plurality of valved discharge ports 24b may be connected between discharge chamber 221 and cylinders 231. Gaskets 32 and 33 are placed between cylinder block 23 and valve plate 24, and between valve plate 24 and rear end plate 22, and seal the matching surfaces of cylinder block 23, valve plate 24 and rear end plate 22.
Further, another wobble plate compressor is disclosed in U.S. Pat. No. 5,165,863 to Taguchi. Referring to FIG. 2, compressor 500 includes cylindrical housing assembly 502 having a cylinder block 502a and a front housing 503 disposed at one end of cylinder block 502a. A crank chamber 510 is enclosed within cylinder block 502a by front housing 503. Rear end plate 531 is forward of crank chamber 510 and attached at the opposite end of cylinder block 502a by a plurality of bolts (not shown). Valve plate 530 is located between rear end plate 531 and cylinder block 502a. Opening 503a is centrally formed in front housing 503 for supporting drive shaft 509 with bearing 508 disposed therein. The inner portion of drive shaft 509 is disposed within the central bore of cylinder block 502a and rotatably supported by bearing 507. Bore 502c extends to the rear surface of cylinder block 502a.
Cam rotor 511 is fixed on drive shaft 509 by a pin member (not shown) and rotates with drive shaft 509. Thrust needle bearing 505 is disposed between the inner end surface of front housing 503 and the adjacent axial end surface of cam rotor 511. Cam rotor 511 has an arm 511b with a pin member 511a extending therefrom. Slant plate 513 is adjacent to cam rotor 511 and has an opening 513a. Drive shaft 509 is disposed through opening 513a. Slant plate 513 comprises an arm 512 having a slot 512a. Cam rotor 511 and slant plate 513 are connected by a pin member 511a. Pin member 511a is inserted in slot 512a to create a hinge joint, which connects cam rotor 511 and slant plate 513. Pin member 511a slides within slot 512a to allow adjustment of the angular position of slant plate 513 with respect to a plane perpendicular to the longitudinal axis of drive shaft 509.
Wobble plate 516 is nutatably mounted on hub 520 of slant plate 513 through bearings 517 and 518. Thus, slant plate 513 rotates with respect to wobble plate 516. Fork-shaped slider 525 is attached to a radially outer peripheral end of wobble plate 516 and is mounted on a sliding rail 524. Sliding rail 524 is disposed between front housing 503 and cylinder block 502a. Fork-shaped slider 525 prevents the rotation of wobble plate 516 when wobble plate 516 nutates along rail 524. Cylinder block 502a may have a plurality of cylinder chambers 522 wherein pistons 523 are disposed. Each of pistons 523 is connected to wobble plate 516 by a corresponding connection rod 515. Accordingly, nutation of wobble plate 516 causes pistons 523 to reciprocate within their respective chambers 522.
Rear end plate 531 may have a peripherally located annular suction chamber 532 and a centrally located discharge chamber 538. Valve plate 530 may have a plurality of valved suction ports 534 linking suction chamber 532 with cylinder chambers 522. Valve plate 530 has a plurality of valve discharge ports 535 linking a discharge chamber 533 with cylinder chambers 522. Suction ports 534 and discharge ports 535 are provided with suitable reed valves (not shown).
Suction chamber 532 may have an inlet portion (not shown) of an external cooling circuit. Discharge chamber 533 may have an outlet portion (not shown) connected to a condenser (not shown) of the cooling circuit. A valve retainer 536 is fixed on a central region of the outer surface of valve plate 530 by bolts 537 and nut 538. Valve retainer 536 prevents excessive bend of the reed valve at discharge port 535 during compression strokes of piston 523. Rear end plate 531 has a capacity control mechanism 540 disposed within a space 542. Capacity control mechanism 540 controls the pressure of crank chamber 510 by regulating the volume of discharge gas that is introduced into the crank chamber 510. The stroke length of the pistons, and, thus, the capacity of the compressor, may be changed by adjusting the slant angle of the wobble plate. The slant angle is changed in response to the pressure differential between the suction chamber and the crank chamber.
Compressors 100 and 500 in the above-mentioned references have elongated slots 13a and 512a formed in arms 13 and 512, respectively. Arms 13 and 512 are connected to rotor 9 of swash plate 4 and rotor 511 of slant plate 513. Further, rotors 9 and 511 are coupled with swash plate 4 and slant plate 513, such that pins 11 and 511a may be slidably disposed in slots 13a and 512a by employing a washer member. Therefore, the arrangements are fairly complex in production. Further, because elongated slots 13a and 512a are formed by a piercing process with machinery, this arrangement is not simple to manufacture and has a high assembling cost.
Further, during the compression and suction stages of these compressors, pins 11 and 511a are axially subjected to the compression reaction force from the pistons. Thus, it is undesirable that bush 8 and cylindrical sleeve 555 are axially subjected to the excessive force, although bush 8 and cylindrical sleeve 555 are supported by the compression reaction force.
One approach to resolve the problem is to expand the widths of elongated slots 13a and 512a in order to intensify the engaging between pins 11/511a and slots 13a/512a. However, expanding the widths of elongated slots 13a and 512a is limited by the design of the compressor.